Messages in this thread Patch in this message | | | Date | Wed, 17 Dec 2014 18:24:43 -0500 | From | Murali Karicheri <> | Subject | Re: [RFC PATCH 1/2] common: dma-mapping: introduce dma_get_parent_cfg() helper |
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On 12/17/2014 04:56 PM, Arnd Bergmann wrote: > On Wednesday 17 December 2014 13:02:23 Murali Karicheri wrote: >> Now, in Kernel, parent device's DMA parameters has to be applied to >> the child as is - to enable DMA support for the device. Usually this >> is happened in places where parent device manually instantiates child >> device such as in drivers/pci/probe.c (pci_device_add() for example). >> >> Now DMA configuration is represented in device data structure not only >> by DMA mask and DMA params, it also includes dma_pfn_offset at least. >> Hence introduce common dma_get_parent_cfg() helper to apply dma >> configuration from parent to child, and use __weak to allow arch to >> override it if needed. >> >> Signed-off-by: Murali Karicheri<m-karicheri2@ti.com> >> --- >> drivers/base/dma-mapping.c | 18 ++++++++++++++++++ >> include/linux/dma-mapping.h | 3 +++ >> 2 files changed, 21 insertions(+) >> >> diff --git a/drivers/base/dma-mapping.c b/drivers/base/dma-mapping.c >> index 9e8bbdd..5322426 100644 >> --- a/drivers/base/dma-mapping.c >> +++ b/drivers/base/dma-mapping.c >> @@ -339,3 +339,21 @@ void dma_common_free_remap(void *cpu_addr, size_t size, unsigned long vm_flags) >> vunmap(cpu_addr); >> } >> #endif >> + >> +int __weak dma_get_parent_cfg(struct device *dev, struct device *parent) >> +{ >> + struct device *temp = parent; >> + >> + if (!temp) >> + temp = dev->parent; >> + >> + if (temp&& is_device_dma_capable(temp)) { >> + dev->dma_mask = temp->dma_mask; >> + dev->coherent_dma_mask = temp->coherent_dma_mask; > > As discussed, setting the pointers like this is always wrong, > so don't do it. > > What's wrong with using arch_setup_dma_ops() from PCI as suggested > previously? > > Arnd
Arnd,
Thanks for the review.
I had originally written a code based on that line as below. But dma-ranges property is also used by ppc and other architectures in the pci device DT node. So I wasn't sure how this code impact PCI driver functionality on those platforms. Hence used a simpler change as all that is needed for keystone is to get the dma_pfn_offset rightly set in the pci slave device.
Initially I had a function implemented as below for this in of_pci.c.
+ * of_pci_dma_configure - Setup DMA configuration for a pci device + * @dev: pci device to apply DMA configuration + * + * Try to get devices's DMA configuration from DT and update it + * accordingly. This is a similar to of_dma_configure() for platform + * devices. + * + */ +void of_pci_dma_configure(struct pci_dev *dev) +{ + struct device *host_bridge, *parent; + struct pci_bus *bus = dev->bus; + u64 dma_addr, paddr, size; + int ret; + + while (!pci_is_root_bus(bus)) + bus = bus->parent; + host_bridge = bus->bridge; + + parent = host_bridge->parent; + if (parent->of_node) { + /* + * if dma-coherent property exist, call arch hook to setup + * dma coherent operations. + */ + if (of_dma_is_coherent(parent->of_node)) { + set_arch_dma_coherent_ops(&dev->dev); + dev_info(&dev->dev, "device is dma coherent\n"); + } + + /* + * if dma-ranges property doesn't exist - just return else + * setup the dma offset + */ + ret = of_dma_get_range(parent->of_node, &dma_addr, &paddr, &size); + if (ret < 0) { + dev_info(&dev->dev, "no dma range information to setup\n"); + printk("no dma range information to setup\n"); + return; + } + + /* DMA ranges found. Calculate and set dma_pfn_offset */ + dev->dev.dma_pfn_offset = PFN_DOWN(paddr - dma_addr); + dev_info(&dev->dev, "dma_pfn_offset(%#08lx)\n", dev->dev.dma_pfn_offset); + } +} +EXPORT_SYMBOL_GPL(of_pci_dma_configure);
and then called from pci/probe.c as
@@ -1527,6 +1528,9 @@ void pci_device_add(struct pci_dev *dev, struct pci_bus *bus) dev->dev.dma_parms = &dev->dma_parms; dev->dev.coherent_dma_mask = 0xffffffffull;
+ /* Get the DMA configuration from root bridge's parent if present */ + of_pci_dma_configure(dev);
If you think this is a better way to implement this, I can work on a patch set using this approach. Let me know.
-- Murali Karicheri Linux Kernel, Texas Instruments
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